[vr] Bail on unhandled code points.

chrome/browser/android/vr_shell/ui_unsupported_mode.h

Index: chrome/browser/android/vr_shell/ui_unsupported_mode.h
diff --git a/chrome/browser/android/vr_shell/ui_unsupported_mode.h b/chrome/browser/android/vr_shell/ui_unsupported_mode.h
new file mode 100644
index 0000000000000000000000000000000000000000..e58ae15a959d288f2e3d9581e33942a315b3f6d0
--- /dev/null
+++ b/chrome/browser/android/vr_shell/ui_unsupported_mode.h
@@ -0,0 +1,20 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_ANDROID_VR_SHELL_UI_UNSUPPORTED_MODE_H_
+#define CHROME_BROWSER_ANDROID_VR_SHELL_UI_UNSUPPORTED_MODE_H_
+
+namespace vr_shell {
+
+// Ensure that this stays in sync with VRUnsupportedMode in enums.xml

[Ilya Sherman, 2017/05/26 22:19:51]

Please document that this enum is used to back an UMA histogram, and should
therefore be treated as append-only.

[Mark P, 2017/05/26 22:29:18]

Here's a good comment fragment:
// These values are written to logs.  New enum values can be added, but existing
// enums must never be renumbered or deleted and reused.

[Ian Vollick, 2017/05/27 00:02:43]

Done.

[Ian Vollick, 2017/05/27 00:02:43]

Sounds great - I've used it directly. Thanks.

+enum UiUnsupportedMode : int {

[Ilya Sherman, 2017/05/26 22:19:51]

nit: Mebbe enum class?

[Ian Vollick, 2017/05/27 00:02:43]

Done.

+  kUnhandledCodePoint = 0,
+
+  // This must be last.
+  kMax,

[Ilya Sherman, 2017/05/26 22:19:51]

Optional nit: Usually, "max" is used as an alias for the last item in an enum,
whereas for histograms we really want more of a "count".  So, I'd suggest
renaming this to "kCount".

[Ian Vollick, 2017/05/27 00:02:43]

Done.

+};
+
+}  // namespace vr_shell
+
+#endif  // CHROME_BROWSER_ANDROID_VR_SHELL_UI_UNSUPPORTED_MODE_H_